Interim Guidelines for the Use
of Self-Consolidating Concrete
in PCI Member Plants
PCI Self-Consolidating Concrete FAST Team
MICHAEL LANIER (Chairman)
BERGER/ABAM Engineers Inc.
CURTIS BADMAN Sika Corporation
JOHN BAREINO Oldcastle Precast, Inc.
KEN BAUR High Concrete Structures
CHRIS BOSTER Fabcon, Inc.
CLINT CALVERT Coreslab Structures
RODNEY CUNNINGHAM Boral Materials Technologies
JOE DACZKO Master Builders
DIANE HUGHES W.R. Grace Corporation
JOHN KAISER Spancrete Industries
GARY KNIGHT W.R. Grace Corporation
CHRISTOPHER LEATON The Bluhm Company
DON LOGAN Stresscon Corporation
EDWARD MANSKY W.R. Grace Corporation
ONDREJ MASEK Sika Chemicals Corporation
RICHARD MILLER University of Cincinnati
FRANK NADEAU Unistress Corporation
DAVID SPRAGUE Master builders
MARTIN VACHON Axim Concrete Technologies, Inc.
MICHAEL WADE Boral Material Technologies
JAMES WAMELINK Axim Concrete Technologies, Inc.
DON YARBROUGH Ross Bryant Associates
Division l - Introduction and Guidelines for SCC Applicability
Division 2 - Guidelines for Qualification of Constituent Materials for SCC and Recommendations for Accomplishing a SCC Mix Design
Division 3 - Guidelines for the Production Qualification of SCC
Division 4 - Guidelines for Quality Control of Fresh SCC and Initiation of Curing
Division 5 - Guidelines for Quality Confirmation of Hardened SCC and Quality Confirmation Fabricated from SCC
Division 6 - Guidelines for Forms, Transport, Placing, Finishing, and Curing
Division 7 - Guidelines for Addressing Performance and Prescriptive Project Specifications and Standards
Appendix 1 - SCC Test Methods
Appendix 2 - SCC Checklist
Appendix 3 - SCC Mix Design Examples
Appendix 4 - Sources for SCC Test Apparatus
In early 2002,
a request was made by the PCI Plant Certification Committee to the Technical
Activities Committee (TAC) to provide more guidance to precast/prestressed
concrete producers on the use of Self-Consolidating Concrete The result
of that request was that TAC formed a Team to address this subject and
charged the Team to guidelines on SCC for industry use. The result of committee
The Interim Guidelines for the Use of Self-Consolidating Concrete (SCC) in Precast/Prestressed Concrete Institute Member Plants is now available from PCI Headquarters. In addition, one hard copy of these guidelines has been sent to the primary contact person in each Producer Member plant.
The FAST Team that was charged with the development of these guidelines included volunteer representatives of admixture suppliers currently active in the provision of admixtures used in the production of SCC in the United States, precast concrete producer representatives that have direct experience in the development of SCC mixes and the use of SCC in precast product manufacture, and representatives of industry consulting engineering firms.
If SCC is being used in a plant or its use is being considered, the committee urges involved producers to obtain copies of the SCC Guidelines, to study them and make them available to plant personnel. SCC can bring important advantages to the precast/prestressed concrete industry; however, as can be seen from a review of the guidelines, SCC is a different type of material than normal high performance concrete, and thus requires attention to a somewhat different set of issues to ensure overall success in its use.
DIVISION 1 - INTRODUCTION
GUIDELINES FOR SCC APPLICABILITY
In the last several years, SCC has gained considerable attention in the
concrete industry. Some important questions have been raised regarding
· Is this a new building material or an extension of our existing concrete technology?
· What are the economics and advantages to the precast/prestressed producer? Is SCC for every producer?
· What levels of technology and skill are required to produce consistent quality SCC?
· What is Self-Consolidating Concrete (SCC)?
One definition of SCC
is given below:
"A highly flowable, yet stable concrete that can spread readily into place and fill the formwork without any consolidation and without undergoing significant separation." [Khayat, Hu and Monty]
In 1983, finding sufficiently skilled workers in Japan who could construct
durable concrete structures became an industry-wide problem. One solution
proposed was to develop concrete that would consolidate under its own weight
and not require additional vibration or skilled workers to fully consolidate
the plastic concrete. Professor Hajime Okamura (University of Tokyo, now
Kochi Institute of Technology) originally advocated SCC in February 1986
and the first success with the material was in 1988.
The ability of concrete to flow around and through reinforcement under only the energy of its own weight (without vibration) without creating blockage is referred to as the passing ability of the mix. This capability, in conjunction with the absence of the noise associated with vibration within a precast/prestressed concrete plant, creates new production opportunities.
SCC is a high performance concrete in the plastic state. It takes less energy to move the material (lower shear stress) (viscosity) and should not separate or segregate. A material that takes less energy to move will require fewer workers or finishers to produce a quality precast/prestressed concrete unit. SCC has the potential to allow reallocation of manpower and increased production with existing resources.
When SCC is placed in a form, its motion may be a creeping movement or a rapid flow. Because of this style of flow, the surface finish between the form and the concrete can be exceptionally smooth, creating a much-improved form finish over conventional concrete. To take advantage of the properties of SCC, new production considerations come into play. For example, an important factor in capturing the finish advantages is the type of form oil used, as this can significantly affect the surface finish.
Demanding form configurations, irregular shapes, thin sections, and heavily reinforced elements can be produced with confidence using SCC. Producing concrete without vibration results in a greatly improved work environment in the plant. Safety hazards are also reduced in the plant, as use of SCC minimizes the need for workers to walk on the top of the form, and eliminates the cords and hoses associated with concrete vibrators. It has been reported that worker absenteeism and accidents have both seen significant reductions when SCC has been introduced into precast production activities.
Concrete forms also benefit from lack of vibration with increased life cycle. Typically, form vibration is one of the elements that lead to form damage, associated repair requirements, and ultimately to form replacement.
1.2 Product Applicability
What is the applicability
of SCC? Where can it be used? Technically, SCC has many advantages over
normal production concrete used in precast/prestressed concrete plants.
It is well suited for producing both vertical and horizontal components
with block-outs and crowded reinforcement. SCC is applicable for production
of architectural and textured surfaces. Some precast plants are reporting
using SCC in nearly 100 percent of their production and expect further
opportunities for SCC with the industry acceptance of an SCC specification.
SCC will require a higher level of quality control, a greater awareness of aggregate gradation, mix water control, and the use of highly advanced high-range water-reducing admixtures and/or viscosity modifiers.
When looking at SCC costs and benefits versus those of conventional concrete, economic analysis should not be restricted to the material cost of the mix alone. The benefits of SCC will filter throughout a plant with savings in production labor, greater form life, fewer bug holes, less patching, improved work environment and the opportunity of changing production methods by eliminating vibration.
Using SCC in plant production provides the opportunity for improved, more efficient operational procedures. An economic study of SCC use for a specific plant needs to span six months to a year to completely analyze the beneficial impact of SCC production, as modified production methods associated with the use of the material, will continue to evolve over time.
1.3 Changing Production Methods to Take Advantage of SCC Properties
It is expected that significant additional advantages will result from
SCC usage as individual producers rethink their production methods in the
context of the characteristics of SCC. For example, can the current methods
of concrete transportation within the plant be changed to take advantage
of the ease of placing SCC?
Can the methods of forming and securing internal reinforcement and hardware be revised because they do not have to withstand the forces associated with the vibration/consolidation process?
Can the time associated with concrete placement be reduced, thus al. lowing more time in the daily cycle for other things? Can more time be made available for curing during the daily production cycle, thus reducing the need for accelerated curing? Are there elements of the current plant layout that the use of SCC will allow to be made more efficient? Can labor be allocated from placement activities to other important activities allowing improvements in efficiency and quality?
1.4 Potential New Product Applications for Elements Cast from SCC
An important aspect of the design of many current precast elements is the
ability to place and consolidate concrete within the form and around the
internal reinforcement, prestressing strand, and hardware that are incorporated
within the element. In some cases, this includes providing space for the
insertion of internal vibrators and assurance that there is sufficient
space to allow concrete flow. Can the increased flowability of SCC ease
any of these constructibility requirements and can element shapes be changed
to advantage (made more efficient as a result?
Can smaller diameter reinforcement on a smaller grid spacing be used to advantage to develop thinner sections that still provide adequate strength and serviceability? Can high strength composite materials be used in combination with thinner sections to produce high value products that are now produced by other segments of industry? SCC may allow the development of new manufacturing processes that can be used to produce new classes of precast concrete elements.
A wide variety of architectural finishes can be accomplished with SCC. As with any new concrete mix, the procedures to attain desired finishes must be developed for new SCC mixes.
If surface finish quality were to be dramatically improved through use of SCC, what new high value products could the precast industry produce? Some examples might higher value cladding, higher value interior finish elements, and items like sinks and bathtubs. The development of SCC guidelines, specifications, and best practices may lead to the use of SCC in mainstream concrete production.
GUIDELINES FOR THE PRODUCTION QUALIFICATION
OF SELF-CONSOLIDATING CONCRETE
Qualification of mix designs
This is where the mixture qualification process becomes important. Essentially, the fluidity of SCC is analogous to economic specification of compressive strength; one should design for only that level that is needed for the successful completion of a project. There are three levels of tests to consider when using SCC.
SCC appears to have significant potential for its use in the precast/prestressed
concrete industry. As with any new material, there are material properties
differences and production process differences that must be understood
and appropriately addressed in both design and production activities.
The development and distribution of the PCI SCC Guidelines is one step in furthering the understanding of this material that will allow its appropriate use in the production of high quality precast/prestressed concrete products that meet all of the needs of the industry's many and varied customers.
The complete report, 135
pages, is available from PCI.
$ 35 - Members, $70 non-members
Call PCI Books & Publications 312-786-0300